As the level of integration of integrated circuitry increases, it is becoming an ever greater challenge to maintain electrical isolation between adjacent electrical devices. For instance, the density of dynamic random access memory (DRAM) has been approximately quadrupled every three years by virtue of advances in DRAM technology. As the device dimensions scale down, it is becoming more and more challenging to maintain electrical isolation (especially cell-to-cell isolation) in the memory array region due to reduction of space for isolation structures. A common isolation structure is a trenched isolation structure (such as, for example, a shallow trench isolation structure), and it is becoming increasingly challenging to form and fill the trenches of such isolation structures within the ever-decreasing real estate available for the structures.
Cell-to-cell isolation is becoming a greater factor in causing failure of integrated circuitry, with such failure frequently being due to leakage around a trenched isolation region. Field implants have been utilized in an attempt to prevent leakage around trenched isolation structures, but such can create problems with refresh.
Cell-to-cell isolation is already problematically challenging, and is expected to become even more challenging for future generations of devices due to the tighter pitch and smaller space available for isolation structures of the future. Accordingly, it is desirable to develop new isolation structures. It would be particularly desirable for such isolation structures to be suitable for cell-to-cell isolation.